The invention concerns a method for detecting and/or monitoring the temperatures of at least two electronic power switches manufactured in particular from a semi-conductor material. In addition the two switching modules are coupled with, e.g. positioned on a common cooling body. The temperature detection and/or monitoring is carried out by means of a temperature model, each of which is associated with one of the switches or switching modules. In the temperature model associated with one of the switches switching and operating parameters are processed in order to calculate the temperature and/or a temperature difference within the relevant switches.
The invention further concerns a temperature emitting electronic power switch assembly that can in particular consists of a converter for electric drives or another power converter. This arrangement is suitable for carrying out the said method and is equipped with two or more switches, in particular power semi-conductor switches, which are coupled with, e.g. positioned on a common cooling body. A calculator calculates a temperature model for each of the switches and records signals representing switching and operating parameters as well as temperature measurements via interfaces. In this way the temperature and/or a temperature difference is calculated in the relevant switch by means of the temperature model activated within the calculator.
A method and an arrangement for a converter with power semi-conductors of the type described above is known from EP 1 193 756 A1. A temperature model that calculates at least the temperature surrounding the cooling body and/or the air supply to the cooling body, an operating parameter and a unit parameter is used here, and temperature differences and/or temperatures are calculated. In the cooling chain of the converter two temperatures are measured in different positions and it is attempted to calculate the temperatures of the same by means of the temperature model in connection with the loss of the power switch. For this it is suggested that two temperature sensors are positioned differently in such a way that the first position provides a substantially lower heat conducting resistance to the switches than the second temperature measuring position. In fact the temperature sensor in the first position measures the temperature of the power semi-conductor switch, and the temperature sensor in the second position measures the temperature of the air supply that is taken in by a fan and directed onto the cooling body to extract heat. One disadvantage of this is however the fact that the temperature distribution within the cooling medium, namely in the fan air supply and also in the cooling body is assumed to be distributed in a homogenous way and that it is further assumed that all semi-conductor power switches of the converter would be at the same temperature and be subject to identical temperature changes.
A method for protecting end sections against over temperatures is known from DE 198 60 762 A1, whereby the end sections are a part of a controller for a combustion engine. The losses of the power switch of the end section, and therefore the temperature of the same, are assumed proportionally as the switch-on time. The temperature is detected by means of a temperature model that takes into consideration at least the internal losses of the controller components. From the control times the actual losses of the individual end sections are calculated.
A means for monitoring the temperature of a thyristor is known from DE 35 36 098 A1, the same being cooled by means of cooling bodies and ambient air. In order not to exceed the maximum temperature on the thyristor semi-conductor the temperature of the ambient air and the losses of the thyristor are recorded. With the aid of a thermic model known as “power semi-conductor, cooling body, cooling medium to ambient air” the temperature at the thyristor is determined.
Chapter 3.2 starting with page 135 of the application handbook 2005/12 of the company SEMIKRON describes the thermic characteristics of semi-conductor switching modules, in particular of IGBT modules. The calculation of the losses of transistor and free diode of an IGBT in particular is described therein and the adherence to a maximum permitted bather layer temperature of 150° C. prescribed. In addition page 145 shows a detailed thermic replacement flow diagram for the calculation of the bather layer temperature. However, this company information does not show how temperature recording and monitoring can be carried out efficiently for an arrangement with a multitude of semi-conductor power switching modules which are commonly used in converters.
It is therefore the purpose of the invention to increase the reliability and accuracy of temperature recordings for all switches for the temperature monitoring of an arrangement with several electronic power switches with the least possible additional effort for all switches.